The barrier to using low-carbon concrete on more jobs isn’t the mix. It’s where the building goes. That’s the finding from an ETH Zurich team publishing in Nature Communications, and it points the fix at building codes rather than at chemistry.
The durability problem with blended cements
There are several ways to cut the embodied carbon of concrete. Blend Portland cement with limestone. Substitute fly ash from coal plants or granulated blast furnace slag from steelmaking. Use microorganisms or enzymes that take up carbon dioxide. All of them work on the carbon side.
All of them also carbonate faster. Low-carbon concrete absorbs more CO2 from the air than conventional concrete, which drops internal alkalinity and strips the passive layer protecting embedded reinforcement. Rebar starts to rust. Since durability provisions in current codes exist specifically to prevent that, the codes end up discouraging the greener mix, and specifiers default back to straight Portland.
What the ETH Zurich corrosion modeling found
Rather than treat corrosion rate as a fixed property of a mix design, the researchers modeled how it develops in service. They ran three concrete formulations through four cities with sharply different climates: Zurich, Bergen, Manaus and Huailai. Local weather data fed a model tracking moisture movement through the concrete and the corrosion that moisture drives.
Wet concrete corroded up to 100 times faster than dry concrete. Differences between the mixes themselves mattered comparatively little. Climate, not chemistry, turned out to be the dominant variable, which means the same low-carbon mix that degrades quickly in Bergen can perform fine in a dry climate.
Why this is a code problem, not a materials problem
Durability requirements are written to apply uniformly across a jurisdiction. That’s administratively simple and, on this evidence, technically wrong. Lead researcher Ueli Angst framed the need as better understanding of how environmentally friendly concretes behave long term under different weather conditions. Calibrate the standard to the structure’s actual location and low-carbon mixes open up across the dry regions where they hold up.
For anyone specifying concrete in the arid Southwest right now, that’s the practical read: the exposure class governing your cover and w/c ratio was probably written for a wetter country than the one you’re building in. Getting that changed runs through ACI committees and adopting jurisdictions, not through a lab. It’s slower than a chemistry breakthrough. It’s also cheaper, and the research is already done.
The study is Albert et al., “Rethinking concrete durability for low-carbon concretes through climate-informed corrosion modelling,” Nature Communications, 2026.